In the prior art, there are devices able to adjust the temperature of the intake air of an internal combustion engine which may be classified into three families. One first family constituted by a thermostatic element, such as a wax capsule, is able by controlling the hot air intake flap to obtain a mixture at an average temperature of 30.degree. C. Now, motorists want to feed the engine with fresh air under a full load and with hot air when the load is light. A second family comprising a pneumatic servomotor for controlling the temperature of the mixture according to the load of the engine is able to resolve this problem. Finally, a third family constituted by devices, such as those of the patent FR 2 367 924 associating a pneumatic servomotor with a wax thermostat, are able to adjust the temperature of the air admitted during operation under a full load when the outside temperature is extremely low.